TL;DR
- Researchers have created DNA-like magnetic nanostructures that form strong inter-helix magnetic bonds. These produce topological textures in the magnetic field, opening the door to the next generation of magnetic devices, and patterning magnetic fields on the nanoscale.
- Engineers have developed a lanthanum hexaboride (LaB6) nanowire-based field emission gun that is installable on an aberration-corrected transmission electron microscope (TEM). This combined unit is able to perform atomic resolution observation at an energy resolution of 0.2 eV — the highest resolution ever recorded for non-monochromatic electron guns — with high current stability of 0.4%.
- Researchers found that the iridescent shimmer that makes birds such as peacocks and hummingbirds so striking is rooted in an evolutionary tweak in feather nanostructure that has more than doubled the range of iridescent colors birds can display. This insight could help researchers understand how and when iridescence first evolved in birds, as well as inspire the development of new materials that can capture or manipulate light.
- Biophysicists have found ways to make and manipulate capsule-like DNA structures that could be used in the development of artificial molecular systems. Such systems could function, for example, inside the human body.
- Researchers have developed a method to stabilize a promising material known as perovskite for cheap solar cells, without compromising its near-perfect performance.
- An international team of researchers has used a unique tool inserted into an electron microscope to create a transistor that’s 25,000 times smaller than the width of a human hair.
- National University of Singapore scientists have developed a general wet-chemistry approach for the scalable and automated synthesis of a library of ultra-high-density single-atom catalysts (UHD-SACs) for 15 common transition metals on chemically distinct carriers via a controlled two-step thermal annealing strategy.
- Researchers have discovered a new method to improve the toughness of materials that could lead to stronger versions of body armor, bulletproof glass and other ballistic equipment. The team produced films composed of nanometer-scale ceramic particles decorated with polymer strands (resembling fuzzy orbs) and made them targets in miniature impact tests that showed off the material’s enhanced toughness. Further tests unveiled a unique property not shared by typical polymer-based materials that allowed the films to dissipate energy from impacts rapidly.
- New research has demonstrated that tiny graphene neural probes can be used safely to greatly improve our understanding of the causes of epilepsy.
- A Christmas tree with a thickness of one atom has been made at DTU. It shows how terahertz measurements can be used to ensure the quality of graphene.
- And more!
Nanotech Market
Nanotechnology deals with the ability to see, understand, measure, predict, produce or control matter at nanoscale (below 100 nanometers). The realm of nanotechnology lies between 0.1 and 100 nanometers, wherein a nanometer is defined as one thousandth of a micron. As a versatile technology with widespread applications in a wide range of end-use sectors, nanotechnology is currently facing a mixed bag of challenges and opportunities as the COVID-19 pandemic continues to spread across the globe. With the world fighting its biggest public health crisis in history, nanotechnology healthcare applications are storming into the spotlight led by the focus on nano intervention in terms of designing effective ways to identify, diagnose, treat and eliminate the spread of COVID-19 infections. Their role as nanocarriers has potential to design risk-free and effective immunization strategies. In the post COVID-19 period, use of nanotechnology solutions in the production of a multitude of devices & products will continue to grow.
Amid the COVID-19 crisis, the global market for Nanotechnology estimated at US$42.2 Billion in the year 2020, is projected to reach a revised size of US$70.7 Billion by 2026, growing at a CAGR of 9.2% over the analysis period. Nanocomposites, one of the segments analyzed in the report, is projected to record a 8.7% CAGR and reach US$35.4 Billion by the end of the analysis period. After a thorough analysis of the business implications of the pandemic and its induced economic crisis, growth in the Nanomaterials segment is readjusted to a revised 10.1% CAGR for the next 7-year period.
Latest News & Researches
Complex free-space magnetic field textures induced by three-dimensional magnetic nanostructures
by Claire Donnelly, Aurelio Hierro-Rodríguez, Claas Abert, Katharina Witte, Luka Skoric, Dédalo Sanz-Hernández, Simone Finizio, Fanfan Meng, Stephen McVitie, Jörg Raabe, Dieter Suess, Russell Cowburn, Amalio Fernández-Pacheco in Nature Nanotechnology
Scientists have used state-of-the-art 3D printing and microscopy to provide a new glimpse of what happens when taking magnets to three-dimensions on the nanoscale — 1000 times smaller than a human hair.
The international team led by Cambridge University’s Cavendish Laboratory used an advanced 3D printing technique they developed to create magnetic double helices — like the double helix of DNA — which twist around one another, combining curvature, chirality, and strong magnetic field interactions between the helices. Doing so, the scientists discovered that these magnetic double helices produce nanoscale topological textures in the magnetic field, something that had never been seen before, opening the door to the next generation of magnetic devices.
Magnetic devices impact many different parts of our societies, magnets are used for the generation of energy, for data storage and computing. But magnetic computing devices are fast approaching their shrinking limit in two-dimensional systems. For the next generation of computing, there is growing interest in moving to three dimensions, where not only can higher densities be achieved with 3D nanowire architectures, but three-dimensional geometries can change the magnetic properties and offer new functionalities.
“There has been a lot of work around a yet-to-be-established technology called racetrack memory, first proposed by Stuart Parkin. The idea is to store digital data in the magnetic domain walls of nanowires to produce information storage devices with high reliability, performance and capacity,” said Claire Donnelly, the study’s first author from Cambridge’s Cavendish Laboratory, who has recently moved to the Max Planck Institute for Chemical Physics of Solids.
“But until now, this idea has always been very difficult to realise, because we need to be able to make three-dimensional magnetic systems and we also need to understand the effect of going to three dimensions on both the magnetisation and the magnetic field.”
“So, over the last few years our research has focused on developing new methods to visualize three dimensional magnetic structures — think about a CT scan in a hospital, but for magnets. We also developed a 3D printing technique for magnetic materials.”
The 3D measurements were performed at the PolLux beamline of the Swiss Light Source at the Paul Scherrer Institute, currently the only beamline able to offer soft X-ray laminography. Using these advanced X-ray imaging techniques, the researchers observed that the 3D DNA structure leads to a different texture in the magnetisation compared to what is seen in 2D. Pairs of walls between magnetic domains (regions where the magnetisation all points in the same direction) in neighbouring helices are highly coupled — and as a result, deform. These walls attract one another and, because of the 3D structure, rotate, “locking” into place and forming strong, regular bonds, similar to the base pairs in DNA.
“Not only did we find that the 3D structure leads to interesting topological nanotextures in the magnetisation, where we are relatively used to seeing such textures, but also in the magnetic stray field, which revealed exciting new nanoscale field configurations!” said Donnelly.
“This new ability to pattern the magnetic field at this length scale allows us to define what forces will be applied to magnetic materials and to understand how far we can go with patterning these magnetic fields. If we can control those magnetic forces on the nanoscale, we get closer to reaching the same degree of control as we have in two dimensions.”
“The result is fascinating — the textures in the DNA-like double helix form strong bonds between the helices, deforming their shape as a result,” explained lead author Amalio Fernandez-Pacheco, former Cavendish Researcher, now working at the Institute of Nanoscience & Materials of Aragón. “But what is more exciting is that around these bonds form swirls in the magnetic field — topological textures!”
Having gone from two to three dimensions in terms of the magnetisation, now Donnelly and her collaborators from the Paul Scherrer Institute and the Universities of Glasgow, Zaragoza, Oviedo, and Vienna will explore the full potential of going from two to three dimensions in terms of the magnetic field.
“The prospects of this work are manyfold: these strongly bonded textures in the magnetic helices promise highly robust motion and could be a potential carrier of information,” said Fernandez-Pacheco. “Even more exciting is this new potential to pattern the magnetic field at the nanoscale, this could offer new possibilities for particle trapping, imaging techniques as well as smart materials.”
Evolution of brilliant iridescent feather nanostructures
by Klara Katarina Nordén, Chad M Eliason, Mary Caswell Stoddard in eLife
The iridescent shimmer that makes birds such as peacocks and hummingbirds so striking is rooted in a natural nanostructure so complex that people are only just beginning to replicate it technologically. The secret to how birds produce these brilliant colors lies in a key feature of the feather’s nanoscale design, according to a study led by Princeton University researchers and published in the journal eLife.
The researchers found an evolutionary tweak in feather nanostructure that has more than doubled the range of iridescent colors birds can display. This insight could help researchers understand how and when brilliant iridescence first evolved in birds, as well as inspire the engineering of new materials that can capture or manipulate light.
As iridescent birds move, nanoscale structures within their feathers’ tiny branch-like filaments — known as barbules — interact with light to amplify certain wavelengths depending on the viewing angle. This iridescence is known as structural coloration, wherein crystal-like nanostructures manipulate light.
“If you take a single barbule from an iridescent feather, cross-section it and put it under an electron microscope, you’ll see an ordered structure with black dots, or sometimes black rings or platelets, within a gray substrate,” said first author Klara Nordén, a Ph.D. student in the lab of senior author Mary Caswell Stoddard, associate professor of ecology and evolutionary biology at Princeton and associated faculty in Princeton’s High Meadows Environmental Institute (HMEI). “The black dots are pigment-filled sacs called melanosomes, and the gray surrounding them is feather keratin. I find these nanoscale structures just as beautiful as the colors they produce.”
Curiously, the melanosome structures come in variety of shapes. They can be rod-shaped or platelet-shaped, solid or hollow. Hummingbirds, for example, tend to have hollow, platelet-shaped melanosomes, while peacocks have rod-shaped melanosomes. But why birds evolved iridescent nanostructures with so many different types of melanosomes has been a mystery, with scientists unsure if some melanosome types are better than others at producing a broad range of vibrant colors.
To answer this question, the researchers combined evolutionary analysis, optical modeling and plumage measurements — all of which allowed them to uncover general design principles behind iridescent feather nanostructures.
Nordén and Stoddard worked with co-author Chad Eliason, a postdoctoral fellow at The Field Museum, to first survey the literature and compile a database of all described iridescent feather nanostructures in birds, which included more than 300 species. They then used a family tree of birds to illustrate which groups evolved the different melanosome types.
There are five primary types of melanosomes in iridescent feather nanostructures: thick rods, thin rods, hollow rods, platelets and hollow platelets. Except for thick rods, all of these melanosome types are found in brilliantly colored plumage. Because the ancestral melanosome type is rod-shaped, previous work focused on the two obvious features unique to iridescent structures: platelet shape and hollow interior.
However, when the researchers evaluated the results of their survey, they realized that there was a third melanosome feature that has been overlooked — thin melanin layers. All four melanosome types in iridescent feathers — thin rods, hollow rods, platelets and hollow platelets — create thin melanin layers, much thinner than a structure built with thick rods. This is important because the size of the layers in the structures is key to producing vibrant colors, Nordén said.
“Theory predicts that there is a kind of Goldilocks zone in which the melanin layers are just the right thickness to produce really intense colors in the bird-visible spectrum,” she said. “We suspected that thin rods, platelets or hollow forms may be alternative ways to reach that ideal thickness from the much larger ancestral melanosome size — the thick rods.”
The researchers tested their idea on bird specimens at the American Museum of Natural History in New York City by measuring the color of iridescent bird plumage that results from nanostructures with different melanosome types. They also used optical modeling to simulate the colors that would be possible to produce with different types of melanosomes. From these data, they determined which feature — thin melanin layers, platelet shape or hollowness — has the greatest influence on the range and intensity of color. Combining the results of the optical modeling and plumage analyses, the researchers determined that thin melanin layers — no matter the shape of the melanosomes — nearly doubled the range of colors an iridescent feather could produce.
“This key evolutionary breakthrough — that melanosomes could be arranged in thin melanin layers — unlocked new color-producing possibilities for birds,” Stoddard said. “The diverse melanosome types are like a flexible nanostructural toolkit, offering different routes to the same end: brilliant iridescent colors produced by thin melanin layers.”
This may explain why there exists such a great diversity of melanosome types in iridescent nanostructures. Iridescent nanostructures likely evolved many times in different groups of birds, but, by chance, thin melanin layers evolved from a thick rod in different ways. Some groups evolved thin melanin layers by flattening the melanosomes (producing platelets), others by hollowing out the interior of the melanosome (producing hollow forms), and yet others by shrinking the size of the rod (producing thin rods).
The findings of the study could be used to reconstruct brilliant iridescence in prehistoric animals, Nordén said. Melanosomes can be preserved in fossil feathers for millions of years, which means that paleontologists can infer original feather color — even iridescence — in birds and dinosaurs by measuring the size of fossilized melanosomes.
“Based on the thick solid rods that have been described in the plumage of Microraptor, for example, we can say that this feathered theropod likely had iridescent plumage much more like that of a starling than that of a peacock,” Nordén said.
The composition of melanosomes and keratin in bird feathers could hold clues for engineering advanced iridescent nanostructures that can efficiently capture or manipulate light, or be used to produce eco-friendly paints that do not require dyes or pigments. Super-black coatings such as Vantablack similarly use nanostructures that absorb and disperse rather than reflect light, similar to the black plumage of species in the birds-of-paradise (Paradisaeidae) family.
Iridescent feathers also could lead to a richer understanding of multifunctional materials, Nordén said. Unlike human-made materials, which are often developed for a single function, natural materials are inherently multipurpose. Melanin not only helps produce iridescence; it also protects birds from dangerous ultraviolet radiation, strengthens feathers and inhibits microbial growth.
Stabilized tilted-octahedra halide perovskites inhibit local formation of performance-limiting phases
by Tiarnan A. S. Doherty, Satyawan Nagane, Dominik J. Kubicki, Young-Kwang Jung, Duncan N. Johnstone,et al in Science
Researchers have developed a method to stabilise a promising material known as perovskite for cheap solar cells, without compromising its near-perfect performance.
The researchers, from the University of Cambridge, used an organic molecule as a ‘template’ to guide perovskite films into the desired phase as they form.
Perovskite materials offer a cheaper alternative to silicon for producing optoelectronic devices such as solar cells and LEDs.
There are many different perovskites, resulting from different combinations of elements, but one of the most promising to emerge in recent years is the formamidinium (FA)-based FAPbI3 crystal.
The compound is thermally stable and its inherent ‘bandgap’ — the property most closely linked to the energy output of the device — is not far off ideal for photovoltaic applications.
For these reasons, it has been the focus of efforts to develop commercially available perovskite solar cells. However, the compound can exist in two slightly different phases, with one phase leading to excellent photovoltaic performance, and the other resulting in very little energy output.
“A big problem with FAPbI3 is that the phase that you want is only stable at temperatures above 150 degrees Celsius,” said co-author Tiarnan Doherty from Cambridge’s Cavendish Laboratory. “At room temperature, it transitions into another phase, which is really bad for photovoltaics.”
Recent solutions to keep the material in its desired phase at lower temperatures have involved adding different positive and negative ions into the compound.
“That’s been successful and has led to record photovoltaic devices but there are still local power losses that occur,” said Doherty. “You end up with local regions in the film that aren’t in the right phase.”
Little was known about why the additions of these ions improved stability overall, or even what the resulting perovskite structure looked like.
“There was this common consensus that when people stabilise these materials, they’re an ideal cubic structure,” said Doherty. “But what we’ve shown is that by adding all these other things, they’re not cubic at all, they’re very slightly distorted. There’s a very subtle structural distortion that gives some inherent stability at room temperature.”
The distortion is so minor that it had previously gone undetected, until Doherty and colleagues used sensitive structural measurement techniques that have not been widely used on perovskite materials.
The team used scanning electron diffraction, nano-X-ray diffraction and nuclear magnetic resonance to see, for the first time, what this stable phase really looked like.
“Once we figured out that it was the slight structural distortion giving this stability, we looked for ways to achieve this in the film preparation without adding any other elements into the mix.”
Co-author Satyawan Nagane used an organic molecule called Ethylenediaminetetraacetic acid (EDTA) as an additive in the perovskite precursor solution, which acts as a templating agent, guiding the perovskite into the desired phase as it forms. The EDTA binds to the FAPbI3 surface to give a structure-directing effect, but does not incorporate into the FAPbI3 structure itself.
“With this method, we can achieve that desired band gap because we’re not adding anything extra into the material, it’s just a template to guide the formation of a film with the distorted structure — and the resulting film is extremely stable,” said Nagane.
“In this way, you can create this slightly distorted structure in just the pristine FAPbI3 compound, without modifying the other electronic properties of what is essentially a near-perfect compound for perovskite photovoltaics,” said co-author Dominik Kubicki from the Cavendish Laboratory, who is now based at the University of Warwick.
The researchers hope this fundamental study will help improve perovskite stability and performance. Their own future work will involve integrating this approach into prototype devices to explore how this technique may help them achieve the perfect perovskite photovoltaic cells.
“These findings change our optimisation strategy and manufacturing guidelines for these materials,” said senior author Dr Sam Stranks from Cambridge’s Department of Chemical Engineering & Biotechnology. “Even small pockets that aren’t slightly distorted will lead to performance losses, and so manufacturing lines will need to have very precise control of how and where the different components and ‘distorting’ additives are deposited. This will ensure the small distortion is uniform everywhere — with no exceptions.”
Capsule-like DNA Hydrogels with Patterns Formed by Lateral Phase Separation of DNA Nanostructures
by Yusuke Sato, Masahiro Takinoue in JACS Au
Biophysicists in Japan have found ways to make and manipulate capsule-like DNA structures that could be used in the development of artificial molecular systems. Such systems could function, for example, inside the human body. The study was a collaboration between Yusuke Sato of Tohoku University and Masahiro Takinoue of the Tokyo Institute of Technology (Tokyo Tech), and the findings were published in the JACS Au.
To make the capsules, the researchers first created two different types of DNA nanostructures. Each type was made using three single-stranded DNA molecules with sticky bits at their ends. Due to differences in their DNA sequences, only similar nanostructures stuck together when the two types were mixed.
Sato and Takinoue then combined the nanostructures in solution with an oily mixture of charged and non-charged molecules. The mixture was first heated and then cooled, and finally examined under a microscope.
The researchers found that water-in-oil droplets had formed, with the DNA nanostructures accumulating at the water-oil interface. The nanostructures came together in different kinds of patch-like patterns, depending on the concentration of each type relative to the other.
The scientists also found that the DNA nanostructures agglomerated in a more homogeneous way when an extra X-shaped DNA nanostructure was added to the mix to connect the two types together.
This worked just as well inside lipid vesicles as in water-in-oil droplets. Sato and Takinoue were also able to separate the DNA capsules from the droplets and vesicles without losing their capsule-like shapes. Finally, they were able to open the capsules and degrade them using specific enzymes.
The findings demonstrate an approach for constructing and modifying DNA capsules that could have a variety of different functions and purposes. For example, they could be used to carry substances to specific target organs, releasing their cargo when exposed to certain enzymes. They could also be made mobile by using DNA nanostructures that can be manipulated to alter the shapes of the capsules. Or they could be modified with proteins or DNA-based molecular devices to make functional compartmental structures, like cellular membranes.
“We believe that functional capsules made from DNA, like the ones we have designed, could provide a new approach for developing capsular structures for artificial cell studies and molecular robotics,” say Sato and Takinoue.
The team will next work on inserting different types of cargo into the capsules, including DNA information processors, and releasing them in response to specific stimuli.
Controlling Toughness of Polymer-grafted Nanoparticle Composites for Impact Mitigation
by Shawn H. Chen, Amanda J. Souna, Stephan Jeffrey Stranick, Mayank Jhalaria, Sanat Kumar, Christopher L Soles, Edwin Chan in Soft Matter
Researchers at the National Institute of Standards and Technology (NIST) and Columbia Engineering have discovered a new method to improve the toughness of materials that could lead to stronger versions of body armor, bulletproof glass and other ballistic equipment.
In a study published in Soft Matter, the team produced films composed of nanometer-scale ceramic particles decorated with polymer strands (resembling fuzzy orbs) and made them targets in miniature impact tests that showed off the material’s enhanced toughness. Further tests unveiled a unique property not shared by typical polymer-based materials that allowed the films to dissipate energy from impacts rapidly.
“Because this material doesn’t follow traditional concepts of toughening that you see in classical polymers, it opens up new ways to design materials for impact mitigation,” said NIST materials research engineer Edwin Chan, a co-author of the study.
The polymers that constitute most of the high-impact plastics today consist of linear chains of repeating synthetic molecules that either physically intertwine or form chemical bonds with each other, forming a highly entangled network. The same principle applies to most polymer composites, which are often strengthened or toughened by having some nonpolymer material mixed in. The films in the new study fall into this category but feature a unique design.
“Mixing together plastics with some solid particles is like trying to mix oil and water. They want to separate,” said Sanat Kumar, a Columbia University professor of chemical engineering and co-author of the study. “The realization we’ve made in my group is: One way to fix that is to chemically tether the plastics to the particles. It’s like they hate each other but they can’t get away.”
The films are made of tiny glass spheres, called silica nanoparticles, each covered with chains of a polymer known as polymethacrylate (PMA). To produce these polymer-grafted nanoparticles (PGNs), Kumar’s lab grew PMA chains on the curved surface of the nanoparticles, rendering one end of each chain stationary.
Shorter, or lower molecular mass, chains on the PGNs are constrained by neighboring chains. The lack of motion means they do not interact much. But higher molecular mass polymers, which fan out farther from the spherical nanoparticles, have more elbow room to move, until they become entangled with other chains. Between these two lengths, there is an intermediate molecular mass where polymers are free to move but are also not long enough to knot up.
This phenomenon was useful for the material’s initial purpose, which was permitting gases to move through it quickly. But Chan and others at NIST sought to find out how this unique property would affect toughness. With the help of Kumar’s lab, the researchers tested samples of varying molecular masses.
“We grew polymeric hair off of the particles from a really short, brush-cut regime to a very long, hippie regime,” said NIST materials research engineer and co-author Chris Soles. “The brush-cut nanoparticles don’t entangle and can pack together, but as the polymers get longer, the distance between nanoparticles expands and the chains between particles start to entangle and form a network.”
At NIST, the researchers opened fire on the PGN composite films of different molecular masses with a technique known as Laser-Induced Projectile Impact Testing, or LIPIT. These high-velocity impact tests involved propelling 10-micrometer-wide (about four-thousandths of an inch) spherical projectiles toward the targets at velocities of nearly 1 kilometer per second (more than 2,200 miles per hour) with a laser.
They determined the velocity of the projectile in transit and on impact through images captured with a camera and strobe light flashing every 100 nanoseconds (billionths of a second). From there, the team had what it needed to calculate the energy it took to tear through the film, a quantity directly tied to toughness.
The authors of the study found that the PGN composite films were generally tougher than solely PMA. But what was perhaps more interesting was that intermediate molecular mass yielded the toughest film.
In purely polymeric materials, longer chains tend to create a greater number of tangles. And more tangles translate to greater toughness, up to the point where the material is completely tied up. However, the LIPIT tests revealed that the films could defy traditional polymer behavior. The toughest samples had chains far shorter than the length for full entanglement, meaning that tangles were not the only factor driving toughness.
Soles and his colleagues suspected that the reason was the decreased packing between the chains at the intermediate molecular masses, which could have created a situation where polymers could wriggle about more freely and create friction with neighboring chains — a potential avenue for dissipating energy from a high impact.
Seeking to pin down the underlying source of the toughness and test their hypothesis, the team members used equipment at the NIST Center for Neutron Research to assess the motion of the polymers.
These tests confirmed that the intermediate molecular mass chains attached to the nanoparticles displayed an ability to move and then reach a relaxed state in just a few picoseconds (trillionths of a second). These enhanced movements of the intermediate chains dissipated energy more readily than either the short (no tangles) or long (highly entangled) PMA chains. This finding backed the team’s intuition, especially when taken along with the LIPIT tests.
High-endurance micro-engineered LaB6 nanowire electron source for high-resolution electron microscopy
by Han Zhang, Yu Jimbo, Akira Niwata, Akihiro Ikeda, Akira Yasuhara, Cretu Ovidiu, Koji Kimoto, Takeshi Kasaya, Hideki T. Miyazaki, Naohito Tsujii, Hongxin Wang, Yasushi Yamauchi, Daisuke Fujita, Shin-ichi Kitamura, Hironobu Manabe in Nature Nanotechnology
The National Institute for Materials Science (NIMS) and JEOL, Ltd. have developed a lanthanum hexaboride (LaB6) nanowire-based field emission gun that is installable on an aberration-corrected transmission electron microscope (TEM). This combined unit is able to perform atomic resolution observation at an energy resolution of 0.2 eV — the highest resolution ever recorded for non-monochromatic electron guns — with a high current stability of 0.4%.
Unsuccessful efforts have been made for more than 20 years to develop field emission guns using theoretically high-performance nano materials. It has been found challenging to integrate a nanowire-based field emission gun into an electron microscope without undermining its physical properties, such as lives and stability. For this reason, commercially available field emission guns are still equipped with tungsten needles developed more than half a century ago.
This NIMS-JEOL research team 1) developed techniques to chemically synthesize and grow high-purity, single-crystal nanowires of LaB6, known to be an excellent electron-emitting hot cathode material, 2) designed an electron source mechanism capable of efficiently emitting electrons and 3) developed techniques to extract a single nanowire and integrate it into an optimized electron source structure.
The LaB6 nanowire-based electron source has a number of advantages: relatively moderate vacuum condition requirements, very high current stability, low extraction voltage, narrow electron beam energy distribution width and high brightness. This electron source may be applicable to the development of next-generation field emission electron microscopes with higher spatial and energy resolution — potentially valuable tools in the semiconductor and medical fields.
Semiconductor nanochannels in metallic carbon nanotubes by thermomechanical chirality alteration
by Dai-Ming Tang et al in Science
An international team of researchers has used a unique tool inserted into an electron microscope to create a transistor that’s 25,000 times smaller than the width of a human hair.
QUT Center for Materials Science co-director Professor Dmitri Golberg, who led the research project, said the result was a “very interesting fundamental discovery” which could lead a way for the future development of tiny transistors for future generations of advanced computing devices.
“In this work, we have shown it is possible to control the electronic properties of an individual carbon nanotube,” Professor Golberg said.
The researchers created the tiny transistor by simultaneously applying a force and low voltage which heated a carbon nanotube made up of few layers until outer tube shells separate, leaving just a single-layer nanotube.
The heat and strain then changed the “chilarity” of the nanotube, meaning the pattern in which the carbon atoms joined together to form the single-atomic layer of the nanotube wall was rearranged.
The result of the new structure connecting the carbon atoms was that the nanotube was transformed into a transistor.
Professor Golberg’s team members from the National University of Science and Technology in Moscow created a theory explaining the changes in the atomic structure and properties observed in the transistor.
Lead author Dr. Dai-Ming Tang, from the International Center for Materials Nanoarchitectonics in Japan, said the research had demonstrated the ability to manipulate the molecular properties of the nanotube to fabricated nanoscale electrical device.
Dr. Tang began working on the project five years ago when Professor Golberg headed up the research group at this center.
“Semiconducting carbon nanotubes are promising for fabricating energy-efficient nanotransistors to build beyond-silicon microprocessors,” Dr. Tang said. “However, it remains a great challenge to control the chirality of individual carbon nanotubes, which uniquely determines the atomic geometry and electronic structure. In this work, we designed and fabricated carbon nanotube intramolecular transistors by altering the local chirality of a metallic nanotube segment by heating and mechanical strain.”
Professor Golberg said the research in demonstrating the fundamental science in creating the tiny transistor was a promising step towards building beyond-silicon microprocessors.
Transistors, which are used to switch and amplify electronic signals, are often called the “building blocks” of all electronic devices, including computers. For example, Apple says the chip which powers the future iPhones contains 15 billion transistors.
The computer industry has been focused on developing smaller and smaller transistors for decades, but faces the limitations of silicon.
In recent years, researchers have made significant steps in developing nanotransistors, which are so small that millions of them could fit onto the head of a pin.
“Miniaturization of transistors down to nanometer scale is a great challenge of the modern semiconducting industry and nanotechnology,” Professor Golberg said. “The present discovery, although not practical for a mass-production of tiny transistors, shows a novel fabrication principle and opens up a new horizon of using thermomechanical treatments of nanotubes for obtaining the smallest transistors with desired characteristics.”
Full-bandwidth electrophysiology of seizures and epileptiform activity enabled by flexible graphene microtransistor depth neural probes
by Bonaccini Calia, A. et al. in Nature Nanotechnology
New research has demonstrated that tiny graphene neural probes can be used safely to greatly improve our understanding of the causes of epilepsy.
The graphene depth neural probe (gDNP) consists of a millimeter-long linear array of micro-transistors imbedded in a micrometer-thin polymeric flexible substrate. The transistors were developed by a collaboration The University of Manchester’s Neuromedicine Lab and UCL’s Institute of Neurology along with their Graphene Flagship partners.
The paper, published today in Nature Nanotechnology, shows that the unique flexible brain probes can be used to record pathological brain signals associated with epilepsy with excellent fidelity and high spatial resolution.
Dr. Rob Wykes of The University of Manchester’s Nanoneuro team says that “application of this technology will allow researchers to investigate the role infraslow oscillations play in promoting susceptibility windows for the transition to seizure, as well as improving detection of clinically relevant electrophysiological biomarkers associated with epilepsy.”
The flexible gDNP devices were chronically implanted in mice with epilepsy. The implanted devices provided outstanding spatial resolution and very rich wide bandwidth recording of epileptic brain signals over weeks. In addition, extensive chronic biocompatibility tests confirmed no significant tissue damage and neuro-inflammation, attributed to the biocompatibility of the used materials, including graphene, and the flexible nature of the gDNP device.
The ability to record and map the full range of brain signals using electrophysiological probes will greatly advance our understanding of brain diseases and aid the clinical management of patients with diverse neurological disorders. Current technologies are limited in their ability to accurately obtain with high spatial fidelity ultraslow brain signals.
Epilepsy is the most common serious brain disorder worldwide, with up to 30% of people unable to control their seizures using traditional anti-epileptic drugs. For drug-refractory patients, epilepsy surgery may be a viable option. Surgical removal of the area of the brain where the seizures first start can result in seizure freedom; however, the success of surgery relies on accurately identifying the seizure onset zone (SOZ).
Epileptic signals span over a wide range of frequencies — much larger than the band monitored in conventionally used scans. Electrographic biomarkers of a SOZ include very fast oscillations as well as infraslow activity and direct-current (DC) shifts.
Implementing this new technology could allow researchers to investigate the role infraslow oscillations play in promoting susceptibility windows for the transition to seizure, as well as improving detection of clinically relevant electrophysiological biomarkers associated with epilepsy.
Future clinical translation of this new technology offers the possibility to identify and confine much more precisely the zones of the brain responsible for seizure onset before surgery, leading to less extensive resections and better outcomes. Ultimately, this technology can also be applied to improve our understanding of other neurological diseases associated with ultraslow brain signals, such as traumatic brain injury, stroke and migraine.
Scalable two-step annealing method for preparing ultra-high-density single-atom catalyst libraries
by Xiao Hai et al in Nature Nanotechnology
National University of Singapore scientists have developed a general wet-chemistry approach for the scalable and automated synthesis of a library of ultra-high-density single-atom catalysts (UHD-SACs) for 15 common transition metals on chemically distinct carriers via a controlled two-step thermal annealing strategy.
Catalysts play an important role in a number of industrial chemical processes and there is an increasing need for more advanced versions to improve their effectiveness. Heterogeneous single atom catalysts (SACs) are a new class of catalysts that consists of isolated metal atoms singly dispersed on the surface of supports. Their unique geometric and electronic properties have the potential to significantly improve selectivity of the targeted catalytic reactions and lower operational costs. Since the concept of SACs was coined in 2011, interest in this class of SACs materials has surged globally focusing on their use to improve the efficiency of chemical transformations for sustainable industrial processes. A fundamental challenge for implementing this pioneering class of catalysts in many technical applications is the lack of synthetic routes to produce them with high surface densities. Achieving the latter is particularly important to maximize the productivity of the catalysts in large scale industrial processes.
A NUS research team led by Prof Jiong Lu from the Department of Chemistry and the Institute for Functional Intelligent Materials, National University of Singapore have addressed this challenging issue by developing a scalable and versatile two-step annealing method for preparing libraries of ultra-high-density SACs. This work is a collaboration involving Prof Javier Pérez-Ramírez from ETH Zurich, Prof Jun Li from Tsinghua University and Dr. Xiaoxu Zhao from Nanyang Technological University (NTU). The method leverages on the control of ligand removal from metal precursors and their associated interactions with the carrier to saturate the material surface with metal atoms.
A selective anchoring mechanism that maximizes the probability of bonding the metal atom to all available coordination sites on the material surface helps to retain a high level of metal coverage. Metal atoms which are not attached are then removed by washing. This prevents potential metal sintering in the subsequent high-temperature annealing step used to remove the residual ligands. The annealing step also allows for the stabilization of the much higher metal contents compared to conventional impregnation routes (see Figure (a)). This scalable synthetic route for the development of UHD-SACs has been demonstrated for 15 common transition metals using chemically distinct carriers of different nature (including nitrogen-doped carbon, polymeric carbon nitride, ceria, alumina and titania) with loading exceeding 20 wt.% (see Figure (b)). In addition, the proposed approach is readily amenable to a standardized, automated protocol (see Figure © and Figure (d)) demonstrating its robustness and provides a viable path to explore a large number of libraries of mono- or multi-metallic catalysts.
The team showed the potential benefits from high-loading of SACs in distinct catalytic systems, which range from electrochemical, thermal and organic catalysis, exemplifying the need to optimize the surface metal density for a specific catalytic application. Moreover, loading-dependent site-specific activity observed in distinct catalytic systems reflects the well-known complexity in heterogeneous catalyst design. This now can be tackled with a library of SACs with widely tunable metal loadings.
Prof Lu said, “Our work has solved long-standing issues in single-atom catalysis, including loading density and scalable fabrication of this pioneering class of UHD-SACs. This is crucial for their industrial implementation in sustainable chemical and energy transformations.”
MISC
- Researchers make the world’s thinnest Christmas tree: A Christmas tree with a thickness of one atom has been made at DTU. It shows how terahertz measurements can be used to ensure the quality of graphene.
- Nanomedicine holds key to beating the never-ending COVID mutation cycle:
Subscribe to Paradigm!
Medium. Twitter. Telegram. Telegram Chat. Reddit. LinkedIn.
Main sources
Research articles
