How to Soften a Diamond

Dr. Lars Pastewka's and Prof. Michael Moseler's team at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg/Germany can now reveal the secret of why it is that diamonds can be machined. The team published its findings in the current online issue ofNature Materials. This work represents major progress in tribology -the research of friction and wear. Despite the great significance for industry the scientific basics of tribology are poorly understood.

Diamonds have been ground by craftsmen for hundreds of years using cast iron wheels studded with fine diamond particles turning at around 30 meters per second at the outer rim. A highly tuned sense of sound and feeling enable an experienced diamond grinder to hold the rough diamond at just the right angle to achieve a smooth and polished surface. The fact that diamonds react directionally has been known for a long time, says Lars Pastewka. The physical phenomenon is known as anisotropy. The carbon atoms in the diamond lattice form lattice planes, some of which are easier to polish than others, depending on the angle at which the diamond is held.

For hundreds of years, researchers have been looking for a logical way of explaining this empirical phenomenon, and have so far been unsuccessful. Equally, no one has been able to explain why it is possible that the hardest material in the world can be machined. The scientists in Freiburg have answered both these questions with the help of a newly developed calculation method.

Michael Moseler explains the method in layman's terms:"The moment a diamond is ground, it is no longer a diamond." Due to the high-speed friction between the rough diamond and the diamond particles in the cast iron wheel, a completely different"glass-like carbon phase" is created on the surface of the precious stone in a mechanochemical process. The speed at which this material phase appears depends on the crystal orientation of the rough diamond."This is where anisotropy comes in," explains Moseler.

The new material on the surface of the diamond, adds Moseler, is then"peeled off" in two ways: the ploughing effect of the sharp-edged diamond particles in the wheel repeatedly scratches off tiny carbon dust particles from the surface -- this would not be possible in the original diamond state, which is too hard and in which the bond forces would be too great. The second, equally important impingement on the normally impenetrably hard crystal surface is due to oxygen (O) in the air. The O₂molecules bond with carbon atoms (C) within the instable, long carbon chains that have formed on the surface of the glassy phase to produce the atmospheric gas CO₂, carbon dioxide.

And how was it possible to determine when and which atoms would detach from the crystalline surface?"We looked extremely closely at the quantum mechanics of the bonds between the atoms at the surface of the rough diamond breaking. We had to analyze the force field between the atoms in detail," explains Lars Pastewka.

If one understands these forces well enough, one can precisely describe -- and model -- how to make and break bonds."This provided the basis for investigations into the dynamics of the atoms at the friction surface between a diamond particle on the wheel and the rough diamond itself," adds Pastewka. He and his colleague Moseler have calculated the paths of around 10,000 diamond atoms and followed them on screen. Their calculations paid off: their model is able to explain all the processes involved in the dusty and long misunderstood method of diamond grinding.

The newly developed model is not only a milestone in the field of diamond research:"It proves also that friction and wear processes can be described precisely with modern material simulation methods ranging from the atomic level to macroscopic objects." emphasizes Prof. Peter Gumbsch, director of the institute. He considers this just as one example of the many questions on wear that industry needs answers to. These questions will be addressed in future by the Fraunhofer IWM within the newly founded MicroTribology CentreµTC under the motto"make tribology predictable."

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Direct Observation of Carbon Monoxide Binding to Metal-Porphyrines

An important characteristic of porphyrins is their conformational flexibility. Recent research has shown that each specific geometric configuration of the metalloporphyrins has a distinct influence on their functionality. In line with the current state of research, the scientists expected only a single CO molecule to bind axially to the central metallic atom. However, detailed scanning tunnel microscopy experiments by Knud Seifert revealed that, in fact, two gas molecules dock between the central metallic atom and the two opposite nitrogen atoms. Decisive is the saddle shape of the porphyrin molecules, in which the gas molecules assume the position of the rider.

The significance of the saddle geometry became apparent in model calculations done by Marie-Laure Bocquet from the University of Lyon. Her analysis helped the researchers understand the novel binding mode in detail. She also showed that the shape of the molecular saddle remains practically unchanged, even after the two gas molecules bind to the porphyrin.

The porphyrins reacted very differently when the researchers replaced the carbon monoxide with stronger-binding nitrogen monoxide. As expected, this binds directly to the central atom, though only a single molecule fits in each porphyrin ring. This has a significant effect on the electronic structure of the carrier molecule, and the characteristic saddle becomes flattened. Thus, the porphyrin reacts very differently to different kinds of gas -- a result that is relevant for potential applications, such as sensors.

Dr. Willi Auwaerter, one of the authors, is thrilled:"What's new is that we actually saw, for the first time, the mechanism on a molecular level. We even can selectively move individual gas molecules from one porphyrin to another." The team aims to explain the physical and chemical processes on surfaces and in nanostructures. Once these fundamental questions are answered, they will take on new challenges: How big is the influence of the central atom? How does the binding change in planar conformations? How can such systems be utilized to implement catalyzers and sensors through controlled charge transfers?

The research was funded by the Deutsche Forschungsgemeinschaft (Cluster of Excellence"Munich Center for Advanced Photonics"), the TUM Institute for Advanced Study, the European Research Council (ERC Advanced Grant MolArt), as well as the Spanish Ministerio de Ciencia E Innovacion. The Leibniz Rechenzentrum of the Bayerische Akademie der Wissenschaften provided computing time. The research group of Professor Barth is member of the Catalysis Research Center (CRC) of the TUM.

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Graphene Grains Make Atom-Thick Patchwork 'Quilts'

The multidisciplinary Cornell collaboration, publishing online Jan. 5 in the journal Nature, focuses on graphene -- a one atom-thick sheet of carbon atoms bonded in a crystal lattice like a honeycomb or chicken wire -- because of its electrical properties and potential to improve anything from solar cells to cell phone screens. But it doesn't grow in perfect sheets; rather, it develops in pieces that resemble patchwork quilts, where the honeycomb lattice meets up imperfectly and creates five- or seven-member carbon rings, rather than the perfect six. Where these"patches" meet are called grain boundaries, and scientists had wondered whether these boundaries would allow the special properties of a perfect graphene crystal to transfer to the much larger quilt-like structures.

To study the material, the researchers grew graphene membranes on a copper substrate (a method devised by another group) but then conceived a novel way to peel them off as free-standing, atom-thick films. Then, with diffraction imaging electron microscopy, they imaged the graphene by seeing how electrons bounced off at certain angles, and using a color to represent that angle. By overlaying different colors according to how the electrons bounced, they created an easy, efficient method of imaging the graphene grain boundaries according to their orientation. And as a bonus, their pictures took an artistic turn, reminding the scientists of patchwork quilts.

"You don't want to look at the whole quilt by counting each thread," said David Muller, professor of applied and engineering physics and co-director of the Kavli Institute at Cornell for Nanoscale Science, who conducted the work with Paul McEuen, professor of physics and director of the Kavli Institute; and Kavli member Jiwoong Park, assistant professor of chemistry and chemical biology."You want to stand back and see what it looks like on the bed. And so we developed a method that filters out the crystal information in a way that you don't have to count every atom."

This new method could apply to other two-dimensional materials and sheds new light on the previously mysterious way that graphene was stitched together at grain boundaries.

Further analysis revealed that growing larger grains (bigger patches) didn't improve the electrical conductivity of the graphene, as was previously thought by materials scientists. Rather, it is impurities that sneak into the sheets that make the electrical properties fluctuate. This insight will lead scientists closer to the best ways to grow and use graphene.

The work was supported by the National Science Foundation through the Cornell Center for Materials Research and the Nanoscale Science and Engineering Initiative, as well as the Air Force Office of Scientific Research through the Multidisciplinary Research Program of the University Research Initiative and a Presidential Early Career Award for Scientists and Engineers. The paper's other contributors were: Pinshane Huang (applied and engineering physics), Carlos Ruiz-Vargas (applied and engineering physics), Arend van der Zande (physics), William Whitney (physics), Mark Levendorf (chemistry), Joshua Kevek (Oregon State), Shivank Garg (chemistry), Jonathan Alden (applied and engineering physics), Caleb Hustedt (Brigham Young University) and Ye Zhu (applied and engineering physics).

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Coiled Nanowires May Hold Key to Stretchable Electronics

"In order to create stretchable electronics, you need to put electronics on a stretchable substrate, but electronic materials themselves tend to be rigid and fragile," says Dr. Yong Zhu, one of the researchers who created the new nanowire coils and an assistant professor of mechanical and aerospace engineering at NC State."Our idea was to create electronic materials that can be tailored into coils to improve their stretchability without harming the electric functionality of the materials."

Other researchers have experimented with"buckling" electronic materials into wavy shapes, which can stretch much like the bellows of an accordion. However, Zhu says, the maximum strains for wavy structures occur at localized positions -- the peaks and valleys -- on the waves. As soon as the failure strain is reached at one of the localized positions, the entire structure fails.

"An ideal shape to accommodate large deformation would lead to a uniform strain distribution along the entire length of the structure -- a coil spring is one such ideal shape," Zhu says."As a result, the wavy materials cannot come close to the coils' degree of stretchability." Zhu notes that the coil shape is energetically favorable only for one-dimensional structures, such as wires.

Zhu's team put a rubber substrate under strain and used very specific levels of ultraviolet radiation and ozone to change its mechanical properties, and then placed silicon nanowires on top of the substrate. The nanowires formed coils upon release of the strain. Other researchers have been able to create coils using freestanding nanowires, but have so far been unable to directly integrate those coils on a stretchable substrate.

While the new coils' mechanical properties allow them to be stretched an additional 104 percent beyond their original length, their electric performance cannot hold reliably to such a large range, possibly due to factors like contact resistance change or electrode failure, Zhu says."We are working to improve the reliability of the electrical performance when the coils are stretched to the limit of their mechanical stretchability, which is likely well beyond 100 percent, according to our analysis."

A paper describing the research was published online Dec. 28 byACS Nano. The paper is co-authored by Zhu, NC State Ph.D. student Feng Xu and Wei Lu, an assistant professor at the University of Michigan. The research was funded by the National Science Foundation.

NC State's Department of Mechanical and Aerospace Engineering is part of the university's College of Engineering.

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Polymer Membranes With Molecular-Sized Channels That Assemble Themselves

Researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have developed a solution-based method for inducing the self-assembly of flexible polymer membranes with highly aligned subnanometer channels. Fully compatible with commercial membrane-fabrication processes, this new technique is believed to be the first example of organic nanotubes fabricated into a functional membrane over macroscopic distances.

"We've used nanotube-forming cyclic peptides and block co-polymers to demonstrate a directed co-assembly technique for fabricating subnanometer porous membranes over macroscopic distances," says Ting Xu, a polymer scientist who led this project."This technique should enable us to generate porous thin films in the future where the size and shape of the channels can be tailored by the molecular structure of the organic nanotubes."

Xu, who holds joint appointments with Berkeley Lab's Materials Sciences Division and the University of California Berkeley's Departments of Materials Sciences and Engineering, and Chemistry, is the lead author of a paper describing this work, which has been published in the journalACS Nano.

Co-authoring the paper with Xu were Nana Zhao, Feng Ren, Rami Hourani, Ming Tsang Lee, Jessica Shu, Samuel Mao, and Brett Helms, who is with the Molecular Foundry, a DOE nanoscience center hosted at Berkeley Lab.

Channeled membranes are one of nature's most clever and important inventions. Membranes perforated with subnanometer channels line the exterior and interior of a biological cell, controlling -- by virtue of size -- the transport of essential molecules and ions into, through, and out of the cell. This same approach holds enormous potential for a wide range of human technologies, but the challenge has been finding a cost-effective means of orienting vertically-aligned subnanometer channels over macroscopic distances on flexible substrates.

"Obtaining molecular level control over the pore size, shape, and surface chemistry of channels in polymer membranes has been investigated across many disciplines but has remained a critical bottleneck," Xu says."Composite films have been fabricated using pre-formed carbon nanotubes and the field is making rapid progess, however, it still presents a challenge to orient pre-formed nanotubes normal to the film surface over macroscopic distances."

For their subnanometer channels, Xu and her research group used the organic nanotubes naturally formed by cyclic peptides -- polypeptide protein chains that connect at either end to make a circle. Unlike pre-formed carbon nanotubes, these organic nanotubes are"reversible," which means their size and orientation can be easily modified during the fabrication process. For the membrane, Xu and her collaborators used block copolymers -- long sequences or"blocks" of one type of monomer molecule bound to blocks of another type of monomer molecule. Just as cyclic peptides self-assemble into nanotubes, block copolymers self-assemble into well-defined arrays of nanostructures over macroscopic distances. A polymer covalently linked to the cyclic peptide was used as a"mediator" to bind together these two self-assembling systems

"The polymer conjugate is the key," Xu says."It controls the interface between the cyclic peptides and the block copolymers and synchronizes their self-assembly. The result is that nanotube channels only grow within the framework of the polymer membrane. When you can make everything work together this way, the process really becomes very simple."

Xu and her colleagues were able to fabricate subnanometer porous membranes measuring several centimeters across and featuring high-density arrays of channels. The channels were tested via gas transport measurements of carbon dioxide and neopentane. These tests confirmed that permeance was higher for the smaller carbon dioxide molecules than for the larger molecules of neopentane. The next step will be to use this technique to make thicker membranes.

"Theoretically, there are no size limitations for our technique so there should be no problem in making membranes over large area," Xu says."We're excited because we believe this demonstrates the feasibility of synchronizing multiple self-assembly processes by tailoring secondary interactions between individual components. Our work opens a new avenue to achieving hierarchical structures in a multicomponent system simultaneously, which in turn should help overcome the bottleneck to achieving functional materials using a bottom-up approach."

This research was supported by DOE's Office of Science and by the U.S. Army Research Office. Measurements were carried out on beamlines at Berkeley Lab's Advanced Light Source and at the Advanced Photon Source of Argonne National Laboratory.

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Fastest Movie in the World Recorded: Method to Film Nanostructures Developed

A"molecular movie" that shows how a molecule behaves at the crucial moment of a chemical reaction would help us better understand fundamental processes in the natural sciences. Such processes are often only a few femtoseconds long. A femtosecond is a millionth of a billionth of a second.

While it is possible to record a single femtosecond picture using an ultra-short flash of light, it has never been possible to take a sequence of pictures in such rapid succession. On a detector that captures the image, the pictures would overlap and"wash out." An attempt to swap or refresh the detector between two images would simply take too long, even if it could be done at speed of light.

In spite of these difficulties, members of the joint research group"Functional Nanomaterials" of HZB and the Technische Universität Berlin have now managed to take ultrafast image sequences of objects mere micrometres in size using pulses from the X-ray laser FLASH in Hamburg, Germany. Furthermore, they chart out a path how their approach can be scaled to nanometer resolution in the future. Together with colleagues from DESY and the University of Münster, they have published their results in the journalNature Photonics.

The researchers came up with an elegant way to descramble the information superimposed by the two subsequent X-ray pulses. They encoded both images simultaneously in a single X-ray hologram. It takes several steps to obtain the final image sequence: First, the scientists split the X-ray laser beam into two separate beams. Using multiple mirrors, they force one beam to take a short detour, which causes the two pulses to reach the object under study at ever so slightly different times -- the two pulses arrive only 0.00000000000005 seconds apart. Due to a specific geometric arrangement of the sample, the pulses gen-erate a"double-hologram." This hologram encodes the structure of the object at the two times at which the X-ray pulses hit., Using a mathematical reconstruction procedure, the researchers can then simply associate the images with the respective X-ray puses and thus determine the image sequence in correct temporal order.

Using their method, the scientists recorded two pictures of a micro-model of the Brandenburg Gate, separated by only 50 femtoseconds."In this short time interval, even a ray of light travels no further than the width of a human hair," says PhD student Christian Günther, the first author of the publication. The short-wavelength X-rays used allow to reveal extremely small detail, since the shorter the wavelength of light you use, the smaller the objects you can resolve.

"The long-term goal is to be able to follow the movements of molecules and nanostructures in real time," says project head Prof. Dr. Stefan Eisebitt. The extremely high temporal resolution in conjunction with the possibility to see the tiniest objects was the motivation to develop the new technique. A picture may be worth a thousand words, but a movie made up of several pictures can tell you about an object's dynamics.

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Breakthrough in Converting Heat Waste to Electricity: Automotive, Chemical, Brick and Glass Industries Could Benefit from Discovery

The material exhibits a high thermoelectric figure of merit that is expected to enable 14 percent of heat waste to electricity, a scientific first. Chemists, physicists and material scientists at Northwestern collaborated to develop the material. The results of the study are published by the journalNature Chemistry.

"It has been known for 100 years that semiconductors have this property that can harness electricity," said Mercouri Kanatzidis, the Charles E. and Emma H. Morrison Professor of Chemistry in The Weinberg College of Arts and Sciences."To make this an efficient process, all you need is the right material, and we have found a recipe or system to make this material."

Kanatzidis, co-author of the study, and his team dispersed nanocrystals of rock salt (SrTe) into the material lead telluride (PbTe). Past attempts at this kind of nanoscale inclusion in bulk material have improved the energy conversion efficiency of lead telluride, but the nano inclusions also increased the scattering of electrons, which reduced overall conductivity. In this study, the Northwestern team offers the first example of using nanostructures in lead telluride to reduce electron scattering and increase the energy conversion efficiency of the material.

"We can put this material inside of an inexpensive device with a few electrical wires and attach it to something like a light bulb," said Vinayak Dravid, professor of materials science and engineering at Northwestern's McCormick School of Engineering and Applied Science and co-author of the paper."The device can make the light bulb more efficient by taking the heat it generates and converting part of the heat, 10 to 15 percent, into a more useful energy like electricity."

The automotive, chemical, brick, glass and any industry that uses heat to make products could make their system more efficient with the use of this scientific breakthrough, said Kanatzidis, who also has a joint appointment at the Argonne National Laboratory.

"The energy crisis and the environment are two major reasons to be excited about this discovery, but this could just be the beginning," Dravid said."These types of structures may have other implications in the scientific community that we haven't thought of yet, in areas such as mechanical behavior and improving strength or toughness. Hopefully others will pick up this system and use it."

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Nanotech Medicine to Rebuild Damaged Parts of Human Body

According to the World Health Organisation (WHO), an estimated 322,000 deaths globally per year are linked to severe injuries from fire and in many of these cases death could have been avoided with surgical intervention.

In this type of intervention, when major burn patients have insufficient skin left to graft on the most damaged part of their body, new skin has literally to be grown from the patient's own skin cells. However, the long delay in growing the skin can expose the burns patient to increased risk of infection and dehydration; so to help those cells to multiply, specialists use a particular kind of component called polymeric material. Because of their extraordinary range of properties, polymeric materials play a ubiquitous role in our daily life. This role ranges from familiar synthetic plastics: plastic bags or yoghurt cups, to natural biopolymers such as wood or proteins that are present in the human body.

New nano-structured materials

It has been known for the last few years that man made synthetic polymeric materials have the potential to grow and multiply human cells. 'About 10 years ago, scientists discovered the important influence that nano-structures had on the way a line of cells would develop. It was the beginning of an entire new scientific field, somewhere between medicine and nanotechnology,' says Professor Johannes Heitz, Senior Research Associate at the University of Linz, Austria and main coordinator of the ModPolEUV project.

In the case of human skin cells, re-implantation of the tissue can be performed once a sufficient amount of skin is obtained, by growing it on a polymeric material surface.

However, in many cases, imperfections in the material structure can make the process relatively long and sometimes inefficient, with cells developing erratically.

The team of Austrian, Czech and Polish scientists involved in the research project managed to develop a new and simple way to create nano-structured materials that would allow a better development of human cells.

The Polish partner in the team, the Military University of Technology of Warsaw, has been in charge of the development of the new laser-based technology called EUV (Extreme Ultra-Violet) that was used for the creation of the nano-structured polymer surfaces. A beam of EUV light formed with a unique mirror developed by the Czech partner REFLEX S.R.O is directed on the surface allowing the creation of new kinds of polymeric materials. This innovative technique allows for a very high degree of precision, from 10 to 20 nanometres, whereas conventional techniques allowed only for a maximal precision level of 100 nanometres. 'One of the newest theories in the field of cell growing is that the smaller the structure, the wider the possibilities to manipulate cells,' says Professor Heitz.

A wide range of human cells

The EUV technique, thanks to its particular level of precision, also allows for the conservation of the material's structure, which was not the case with other methods used to modify the polymer. 'A regular structure is essential if the material is to be used for the purpose of growing human cells,' says Dr Henryk Fiederowicz, Professor at the Military University of Technology.

The story does not end there. Nano-structures built through the EUV technique have the ability to influence the behaviour of organic cells and different kind of cells can be grown better and faster depending on the type of polymer surface used.

The variety of material used to grow human stem cells will determinate the way cells will differentiate, meaning that they will transform into another human cell type. In other words: 'Using one type of polymer material or another will help you grow different types of muscle, nerves, cells adapted to a human heart, bone or any other part of the human body,' says Professor Heitz.

Thanks to their affinity to human tissue and cells, polymeric materials could also be used for designing entire artificial implants. Indeed, many types of implants are already being made out of polymer materials, such as heart valves and bloods vessels. Using the EUV technique would reduce the odds of implant rejection, as the range of new materials created could be adapted to interact perfectly with specific parts of a patient's body.

Broad applications

All partners agree on the fact that EUREKA has helped them to find elsewhere in Europe the expertise and skills unavailable in their own countries. The next step is to bring their innovation to the market.

The Military Institute of Technology has already handled several EUV installations to laboratories in the USA, Germany, the Czech Republic, France, Japan, China and South Korea. It is now preparing for a full commercial phase, in partnership with the Polish company PREVAC, a leader in the market of high-precision instruments.

Applications of this novel technique could go far beyond nano-medicine and bio-technologies. An important potential market could be the one of micro-electronics, with its ever-expanding need for high-precision lithography; applications could be proposed to every type of industry where nano-structures are used. For instance, in micro-mechanics, integrated optics, wear reduction or the production of nano-composite materials.

For researchers at Linz University, the cell-growing technology is still in a testing phase and Professor Heitz prefers not to be overwhelmed by enthusiasm, even though he concedes that results have been 'very encouraging so far'. 'The interaction of cells with which structure dimensions are below 100 nanometres is currently the topic of a huge international effort,' he says. Despite the importance of the innovation 'our contribution is very small when compared to the many other laboratories working in this field at the moment'.

According to Professor Heitz, 'recreating whole organs is still a scientist's dream'. Yet the outcome of the E! 3892 ModPolEUV project might just have brought the dream a little closer to reality.

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Nanoscale Rope: Complex Nanomaterials That Assemble Themselves

Berkeley Lab scientists have developed a nanoscale rope that braids itself, as seen in this atomic force microscopy image of the structure at a resolution of one-millionth of a meter.

Their work is the latest development in the push to develop self-assembling nanoscale materials that mimic the intricacy and functionality of nature's handiwork, but which are rugged enough to withstand harsh conditions such as heat and dryness.

Although still early in the development stage, their research could lead to new applications that combine the best of both worlds. Perhaps they'll be used as scaffolds to guide the construction of nanoscale wires and other structures. Or perhaps they'll be used to develop drug-delivery vehicles that target disease at the molecular scale, or to develop molecular sensors and sieve-like devices that separate molecules from one another.

Specifically, the scientists created the conditions for synthetic polymers called polypeptoids to assemble themselves into ever more complicated structures: first into sheets, then into stacks of sheets, which in turn roll up into double helices that resemble a rope measuring only 600 nanometers in diameter (a nanometer is a billionth of a meter).

"This hierarchichal self assembly is the hallmark of biological materials such as collagen, but designing synthetic structures that do this has been a major challenge," says Ron Zuckermann, who is the Facility Director of the Biological Nanostructures Facility in Berkeley Lab's Molecular Foundry.

In addition, unlike normal polymers, the scientists can control the atom-by-atom makeup of the ropy structures. They can also engineer helices of specific lengths and sequences. This"tunability" opens the door for the development of synthetic structures that mimic biological materials' ability to carry out incredible feats of precision, such as homing in on specific molecules.

"Nature uses exact length and sequence to develop highly functional structures. An antibody can recognize one form of a protein over another, and we're trying to mimic this," adds Zuckermann.

Zuckermann and colleagues conducted the research at The Molecular Foundry, which is one of the five DOE Nanoscale Science Research Centers premier national user facilities for interdisciplinary research at the nanoscale. Joining him were fellow Berkeley Lab scientists Hannah Murnen, Adrianne Rosales, Jonathan Jaworski, and Rachel Segalman. Their research was published in a recent issue of theJournal of the American Chemical Society.

The scientists worked with chains of bioinspired polymers called a peptoids. Peptoids are structures that mimic peptides, which nature uses to form proteins, the workhorses of biology. Instead of using peptides to build proteins, however, the scientists are striving to use peptoids to build synthetic structures that behave like proteins.

The team started with a block copolymer, which is a polymer composed of two or more different monomers.

"Simple block copolymers self assemble into nanoscale structures, but we wanted to see how the detailed sequence and functionality of bioinspired units could be used to make more complicated structures," says Rachel Segalman, a faculty scientist at Berkeley Lab and professor of Chemical and Biomolecular Engineering at University of California, Berkeley.

With this in mind, the peptoid pieces were robotically synthesized, processed, and then added to a solution that fosters self assembly.

The result was a variety of self-made shapes and structures, with the braided helices being the most intriguing. The hierarchical structure of the helix, and its ability to be manipulated atom-by-atom, means that it could be used as a template for mineralizing complex structures on a nanometer scale.

"The idea is to assemble structurally complex structures at the nanometer scale with minimal input," says Hannah Murnen. She adds that the scientists next hope is to capitalize on the fact that they have minute control over the structure's sequence, and explore how very small chemical changes alter the helical structure.

Says Zuckermann,"These braided helices are one of the first forays into making atomically defined block copolymers. The idea is to take something we normally think of as plastic, and enable it to adopt structures that are more complex and capable of higher function, such as molecular recognition, which is what proteins do really well."

X-ray diffraction experiments used to characterize the structures were conducted at beamlines 8.3.1 and 7.3.3 of Berkeley Lab's Advanced Light Source, a national user facility that generates intense x-rays to probe the fundamental properties of substances. This work was supported in part by the Office of Naval Research.

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Nanoworld in Color: Tiny Lens Arrays Can Record or Project Sharp Images

Lights off -- projector on. Lecture theaters, conference halls and seminar rooms currently have to be darkened if the speaker wants to project a presentation on screen. Unfortunately, the attention of the listeners goes off with the lights, and tiredness takes over. A new technique promises to remedy this situation. The projectors of the futur will not only be small and easy to use but also shine so brightly that the images appear sharp and clear, even in a sun-filled room.

The image illuminating the wall of the Fraunhofer exhibition stand at nano tech 2011 will be produced by a luminous cube. The prototype of the new projector consists of an optical system just eleven millimeters square and three millimeters thick through which a powerful LED lamp shines. The images are amazingly sharp, the colors brilliant -- all thanks to micro and nanotechnology."The special thing about the new projection technology is that the image is already integrated in the microoptics. The pixels measuring just a hundred nanometers or so are stored in a chromium layer under the lens array. Such a microarray has around 250 microlenses, and under each lens there is a microimage. When all of them are projected onto the wall together, a high-quality complete image is produced from an extremely small projector," explains Marcel Sieler, physicist at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena.

This pocket-sized technology has the potential to replace not only overhead and digital projectors but also cameras."The commercial prospects for ultra-flat microoptical systems are excellent because they open up numerous new applications -- like minicameras or miniprojectors" enthuses Dr. Michael Popall from the the Fraunhofer Institute for Silicate Research ISC. He adds:"The leap in manufacturing quality achieved in recent months can be compared to the advance in television from the cathode ray tube to HDTV." The IOF scientists have also developed a projector that is not much bigger than a box of matches. It can project presentations, video clips and movies from a cell phone or laptop onto any wall -- at home, in the office or out and about. Ultra-flat cameras that are ideal for area or production monitoring in exposed locations are another application which will be demonstrated in Tokyo.

A special material composition has been developed by researchers at ISC for the manufacture of the microlens arrays used in all these applications. Organic carbon-hydrogen and oxygen compounds are enveloped in an inorganic matrix of silicon oxide or titanium oxide. This prevents the embedded plastics from changing chemically over the course of time. Such ORMOCER^®s are insensitive to mechanical and thermal loadings. Incidentally, the formula for stabilizing sensitive compounds is very old: The ancient Mayas mixed their natural indigo dye, which normally bleaches quickly in the sun, with a clay mineral to render it fast. As a result, the blue dye they used to decorate the walls of their houses and temples lasted for more than a thousand years.

The method employed by the Mayas was very effective but rather crude compared with modern techniques."Today we can control the chemical bonding of the inorganic and organic substances with nanometer precision," states Popall."Development of the material, however, is only one part of the puzzle. The shaping process and the technology needed to control it play a crucial role in lens manufacture. It was only through close cooperation between chemists and physicists at Fraunhofer that we succeeded in producing the arrays, substrates and components needed for extremely flat, high-quality optics." The resolution attainable is now almost as high as that of high-quality glass optics -- but using significantly less material and space. What's more, the new material can be mass produced, which keeps the costs much lower.

Small is beautiful is the principle for the new optical world. The days of suitcase-sized projectors will be therefore numbered.

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Highly Ordered Artificial Spin Ice Created Using Nanotechnology

Scientists from the University of Leeds, the US Department of Energy's Brookhaven National Laboratory and the UK Science and Technology Facilities Council's Rutherford Appleton Laboratory say the breakthrough will allow them to study in much greater detail a scientific phenomenon known as 'magnetic monopoles', which are thought to exist in such structures. Their findings are published November 28 in the journalNature Physics.

Artificial spin ice is built using nanotechnology and is made up of millions of tiny magnets, each thousands of times smaller than a grain of sand. The magnets exist in a lattice in what is known as a 'frustrated' structure. Like water ice, the geometry of the structure means that all of the interactions between the atoms cannot be satisfied at the same time.

"It's like trying to seat alternating male and female diners around a table with an odd number of seats -- however much you re-arrange them you will never succeed," said Dr Christopher Marrows from the University of Leeds, co-author of the paper.

In spin ice, magnetic dipoles with a north and south pole are arranged in tetrahedron structures. Each dipole has magnetic moments, similar to the protons on H2O molecules in water ice, which attract and repel each other. Consequently, the dipoles arrange themselves into the lowest possible energy state, which is two poles pointing in and two pointing out.

Dr Marrows said:"Spin ices have created a lot of excitement in recent years as it has been realised that they are a playground for physicists studying magnetic monopole excitations and Dirac string physics in the solid state. However, until now all of the samples of these artificial structures created in the lab have been what we call 'jammed'.

"What we have done is find a way to un-jam spin ice and get it into a well-ordered ground state known as thermal equilibrium. We can then freeze a sample into this state, and use a microscope to see which way all the little magnets are pointing. It's the equivalent of being able take a picture of every atom in a room as it allows us to inspect exactly how the structure is configured."

Jason Morgan, PhD student at the University of Leeds and lead author of the paper, was the first member of the team to observe the sample in equilibrium. He said:"Getting the sample to self-order in such a way has never been achieved experimentally before and for a while had been considered impossible. But when we looked at the sample using magnetic force microscopy and saw this beautiful periodic structure we knew instantly that we had achieved an ordered ground state."

The researchers have also been able to observe individual excitations out of this ground state within their sample, which they say is evidence for monopole dynamics within the lattice.

Magnetic monopoles -- magnets with only a single north or south pole¬¬- are former hypothetical particles that are now thought to exist in spin ice. There is hope among scientists that understanding these monopoles in more detail could lead to advances in a novel technology field known as 'magnetricity' -- a magnetic equivalent to electricity.

Co-author Sean Langridge, a Science and Technology Facilities Council (STFC) Fellow and visiting Professor at the University of Leeds, added:"In the naturally occurring spin-ice systems this ground state is predicted but has not been experimentally observed.

"Now that is has been observed in an artificial system the next step is to observe dynamically the excitations from this ground state. We can only do this by controlling the interactions with state of the art lithographic techniques. This level of control will provide an even greater level of understanding in this fascinating system."

The team created"artificial" spin ice samples at Brookhaven using a state-of-the-art nanotechnology tool called an electron beam writer. A similar£4 million facility is shortly to be opened at the University of Leeds which will be unique to the UK and will allow continued collaboration with the researchers at Brookhaven.

The research was funded by the Engineering and Physical Sciences Research Council, the Science and Technology Facilities Council, and the US Department of Energy's Office of Science .

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Oxidation Mechanisms at Gold Nanoclusters Unraveled

"This is vital if we want to design oxidation catalysts that could use ambient oxygen in the reaction process. Catalysts that function at low temperatures are significant in terms of energy efficiency in the future," says Academy Research Fellow Karoliina Honkala at the Nanoscience Centre (NSC) of the University of Jyväskylä.

The researchers at the NSC show new evidence from computational studies that supported nanometer-sized gold clusters can completely break the O-O bond by formation of a novel one-dimensional gold-oxide phase at the boundary of the cluster. This mechanism is predicted to dominate at ambient conditions of one atmospheric pressure and room temperature.

The study was published in September inAngewandte Chemie,the leading international journal in chemistry. The study is part of Karoliina Honkala's Academy of Finland Academy Researcher project and it was conducted in cooperation with Professor Hannu Häkkinen. The computational work was facilitated by extensive resources from the Finnish IT Center for Science, CSC.

In the study, researchers exposed the monolayer-thick gold clusters to a variable number of oxygen molecules. It was found that even one gold cluster can effectively adsorb multiple oxygen molecules at the boundaries of the cluster, simultaneously weakening (stretching) the O-O bond by transferring electrons to the oxygenmolecules. Taking into account the effects of temperature and ambient pressure, the calculations predicted that the oxygen molecules will completely dissociate and the oxygen and gold atoms will form one-dimensional alternating chains at the cluster boundary. The oxygen atoms in these chains are negatively and the gold atoms positively charged, creating a system that is reminiscent to a one-dimensional gold-oxide chain. These chains are expected to be the highly catalytically active part towards conversion of carbon monoxide to carbon dioxide at room temperature.

Researchers Pentti Frondelius, Hannu Häkkinen and Karoliina Honkala have studied monolayer-thick gold clusters with 10-20 atoms, supported by thin magnesium oxide films that were grown on silver metal. These systems can be prepared experimentally, and last year the Jyväskylä group published a joint study with Professor Hans-Joachim Freund from the Fritz-Haber Institute in Berlin to characterize atomic and electronic structures of gold clusters in such systems.

Intensive experimental work since the early 1980s has indicated that gold nanoparticles exhibit unexpected catalytic activity towards many industrially important chemical reactions that involve activation of atomic bonds inside oxygen or hydrocarbon molecules. Room-temperature formation of carbon dioxide (CO₂)from carbon monoxide (CO) and oxygen molecule (O₂) is one of the most extensively studied processes. A number of different factors have been suggested to contribute to the ability of gold particles to activate the O-O bond, which is considered to be the key reaction step.

"The study now published provides us with a new approach to the problem. The formation of gold oxide, that is, the oxidation of gold, is in contradiction with the known properties of macroscopic gold metal. On the nanometer scale, however, everything seems to be possible," Professor Häkkinen says.

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